Eastern Europe endured the political and economic oppression of Communism for some 40 years — until the revolutions of 1989. But human freedom wasn't the only victim of the Communist regimes. The environment, too, suffered greatly under centrally planned economies that put a priority on production quotas and developing heavy industries while providing no incentives for conservation or pollution controls. Now two huge tasks confront Eastern Europeans as they try to bring order to their countries: They must energize crippled economies and find the resources to clean up four decades of profligate pollution. Western nations are providing help, but far less than is needed. Some experts worry that without more aid, some countries in the region may not hold together under the economic stresses.